Synchronized Switch Harvesting On Inductor Research Articles

Multimodal piezoelectric energy harvesting on a thin plate integrated with SSHI circuit: an analytical and experimental study

Multimodal piezoelectric energy harvesting can be achieved by integrating piezo-patch harvesters into plate-like structures available in marine, aerospace, and automotive applications. A synchronized switch harvesting on inductor (SSHI) interface as the harvesting circuit has been well studied for cantilever beams, considering the single vibration mode of the structure. However, integrating a two-dimensional electromechanical structure with a SSHI circuit for multimodal energy harvesting is missing in the literature. This paper evaluates the performance of the SSHI interface integrated with a piezoelectric energy harvester (PEH) on a plate-like host structure. The analytical solution is developed based on an equivalent impedance approach to predict the steady-state electrical response of the harvester as a closed-form solution. The experiments are conducted to validate the analytical solution for the system’s first and second vibration modes. The experimental results reveal that integration of SSHI to a plate-like harvester introduces a multi-switching behavior rather than a standard single-switching behavior. Due to the multimodal vibrational characteristics of the plate, the circuit switch is triggered several times at each half period of the vibration, which increases the energy dissipation of the circuit and thus reduces the output voltage. On the other hand, single switching at each half period of the vibration happens for lower piezoelectric voltage levels. This is the desired behavior of the SSHI circuit where the analytical prediction matches with the experimental data. Finally, the energy harvesting performance of the SSHI circuit is compared against the standard rectifier, showing 183% and 134% power output enhancement for the first and second vibration modes, respectively.

A new multi-piezoelectric input synchronized switch harvesting on inductor circuit

This paper has proposed a multi-piezoelectric input synchronized switch harvesting on inductor (MI-SSHI) circuit. The MI-SSHI circuit is mainly composed of an extreme detector unit and synchronized switch harvesting on inductor (SSHI) units. The extreme detector unit generates real-time control signals. Since the principle of SSHI circuit, each voltage on piezoelectric element can be switched at different instant in a period. In this paper, two piezoelectric element inputs are selected as an example. The experimental result validates that the output power of the MI-SSHI circuit is improved by 11.67%, in comparison to the traditional S-SSHI circuit.

Performance Optimization of SSHC Rectifiers for Piezoelectric Energy Harvesting

In the past decades, inductor-based synchronized switch harvesting on inductor (SSHI) rectifiers have been widely employed in many active rectification systems for piezoelectric energy harvesting. Although SSHI rectifiers achieve high energy extraction performance compared to passive full-bridge rectifier (FBR), the performance greatly depends on the inductor employed. While a larger inductor can achieve higher performance, the system form factor is also increased, which is counter to system miniaturization in many applications. To solve this issue, an efficient synchronized switch harvesting on capacitors (SSHC) rectifier was proposed recently. Instead of using large inductors, the SSHC rectifier employs on-chip or off-chip flying capacitors to achieve comparable or higher performance. In previous studies, the flying capacitors are chosen equal to the inherent capacitance of the piezoelectric transducer (PT) to achieve 1/3 voltage flipping efficiency <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$(\eta _{F})$ </tex-math></inline-formula> for a 1-stage SSHC rectifier and 4/5 flipping efficiency for a 8-stage SSHC rectifier. This brief presents that the flipping efficiency can be further increased to 1/2 for a 1-stage SSHC rectifier if the flying capacitor is chosen to be much larger than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$C_{P}$ </tex-math></inline-formula> and the 4/5 flipping efficiency can be achieved by employing only 4 flying capacitors.

High Gain, Load-Tolerant Self-Powered Series–Parallel Synchronized Switching Technique for Piezoelectric Energy Harvesting

In the framework of autonomous wireless devices ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e.g.</i> , sensors) powered by energy available from their surrounding environment, this article exposes a technique combining the so-called series and parallel Synchronized Switch Harvesting on Inductor (SSHI) approaches for piezoelectric energy harvesting. More specifically, the proposed circuit consists in switching the piezoelectric element on two inductors, one in series between the piezoelement and the energy extraction stage (rectifier bridge) and the other one in parallel with the rectifier. This, therefore, allows several energy transfer processes to occur per half period, even when the switching process is finished. Based on numerical analysis supported by experimental validations, it is shown that such a technique permits a significant widening of the effective load and rectified voltage ranges, but also, under particular conditions, a power output magnification that is even larger than in the sole SSHI case.

Efficient self-powered piezoelectric energy harvesting interface circuit with wide rectified voltage

Synchronized Switching Harvesting on Inductor (SSHI) and Synchronous Electric Charge Extraction (SECE) are two classic interface circuit techniques for Piezoelectric energy harvesting. But the former has high peak output power with narrow rectified voltage range, while the latter has wide rectified voltage range with lower peak output power. This paper presents a self-powered interface circuit for piezoelectric energy harvesting to achieve a good balance between the two. The proposed interface circuit is based on the Series-SSHI (S–SSHI) and SECE. The circuit proposed can harvest energy through S–SSHI and SECE in positive and negative half cycles, respectively. Moreover, the figure of merit (FOM), optimal rectified voltage range (ORVR) and region of interest (SRoI) of simulation and experiment results are discussed. The maximum FOM of the proposed circuit is as high as 2.15, which is 1.68 times that of the SECE, and it can reach 6 times the ORVR of the S–SSHI. SRoI factor of the proposed circuit show that the proposed method has better performance. In addition, the circuit shows a simpler implementation compared with state-of-the-art designs.

Nonlinear finite element system simulation of piezoelectric vibration-based energy harvesters

Piezoelectric vibration-based energy harvesters consist of an electromechanical structure and an electric circuitry, influencing each other. We propose a novel approach that allows a finite element based system simulation of nonlinear electromechanical structures coupled to nonlinear electric circuitries. In the finite element simulation the influence of the electric circuit on the electromechanical structure is considered via the vector of external forces, using an implicit time integration scheme. To demonstrate the applicability of the new simulation method an active power circuit is considered. Several examples of piezoelectric vibration-based energy harvesters, connected to standard or synchronized switch harvesting on inductor (SSHI) circuits, showing linear or nonlinear mechanical behavior, are studied to validate the proposed simulation method against numerical results reported in the literature. The advocated method allows for consistent and efficient simulations of complete nonlinear energy harvesters using only one software tool.

Synchronized switch piezoelectric energy harvesting using rotating magnetic ball and reed switches

Synchronized switch harvesting on inductor (SSHI) interface circuit has been developed to boost the harvesting capability of piezoelectric energy harvesters (PEHs). Although some electronic self-powered peak-detector and switching circuits have been proposed to support the practical realization of SSHI, the energy dissipation and voltage drops in transistors and diodes of the self-powered circuits might significantly deteriorate the actual energy harvesting performance. Some mechatronic designs were proposed as well. However, most of their switches are activated by touch impacts, which might introduce undesired high-order vibrations to the main structure. In this paper, rather than using the impact-engaged strategy discussed in the literature, a new mechanism using a magnetic ball for vibration synchronization and reed switches for switching operation is proposed. A PEH shunted to an SSHI interface circuit using the proposed mechatronic approach has been prototyped. Since the peak-detection and switching operations are completed by a mechanical mechanism, less passive electrical components, which consume extra energy, are required in our proposed design. Therefore, the overall energy harvesting performance is improved. Numerical simulations and experimental tests have validated the feasibility of the proposed design. The experimental results have shown that the power output produced by the proposed mechatronic self-powered SSHI design can be increased by and , as compared with the cases using a benchmark standard energy harvesting bridge rectifier and an electronic self-powered SSHI solutions, respectively. Moreover, owing to the new mechatronic design, the auxiliary mechanical components are embedded in the tip block of the cantilevered PEH, rendering the whole system to be a compact design.

Enhancement of surge-induced synchronized switch harvesting on inductor strategy

We propose and demonstrate a novel method to enhance vibration harvesting based on surge-induced synchronized switch harvesting on inductor (S3HI). S3HI allows harvesting of a large amount of energy even from low-amplitude vibrations by inducing a surge voltage during the voltage inversion of a synchronized switch harvesting on inductor (SSHI). The surge voltage and the voltage amplification from the conventional voltage inversion improve energy harvesting. S3HI modifies SSHI by both rewiring the circuit without adding components and using a novel switching pattern for voltage inversion, thus maintaining the simplicity of SSHI. We propose a novel switching strategy and circuit topology and analyze six methods that constitute the S3HI family, which includes traditional S3HI and high-frequency S3HI. We demonstrate that the six methods suitably harvest energy even from low-amplitude vibrations. Nevertheless, the harvestable energy per vibration cycle depends on the switching pattern and storage-capacitor voltage. The use of the proposed switching strategy, which allows energy harvesting before energy-dissipative voltage inversion, substantially increases the harvestable energy per vibration cycle. In the typical case considered in this study, the said increase is on the order of 11%–31% and 15%–450% compared to the traditional and existing high-frequency S3HI methods, respectively, depending on the storage-capacitor voltage. Additionally, the proposed circuit can be used as a traditional circuit. It could be considered a promising alternative to S3HI methods owing to its potential auto-reboot capability, which is not found in traditional S3HI circuit.

Enhancing output power of rotational electret energy harvester by synchronized switch harvesting on inductor

A nonlinear interface circuit, known as synchronized switch harvesting on inductor (SSHI), for in-plane rotational electret kinetic energy harvesters (EHs) was developed. An explicit generator model is derived to verify the applicability of SSHI, which was originally proposed for the piezoelectric EH, on an in-plane electret EH. Experimentally, 505 μW was harvested with SSHI at a rectified voltage of 142 V for an in-plane rotational electret EH rotating at 1 rps, which is 2.47 times of that with a full-bridge rectifier, and which is in good agreement with the simulation result. The circuit efficiency and criteria for the inductor selection were clarified through circuit analysis based on spice simulation. It is found that the power dissipation of voltage-divider and rectification diodes becomes pronounced as the load voltage increases, constraining the efficiency. The inductor, which usually dominates the circuit volume, can be miniaturized for electret EHs, because the voltage inversion ratio, a benchmark of the SSHI performance, turns out to be insensitive to the series resistance of the inductor. The self-powering ability of the proposed circuit is also presented.

A Low-Profile Autonomous Interface Circuit for Piezoelectric Micro-Power Generators

This paper presents a low-profile and autonomous piezoelectric energy harvesting system consisting of an extraction rectifier and a maximum power point tracking (MPPT) circuit for powering portable electronics. Synchronized switch harvesting on capacitor-inductor (SSHCI) technique with its unique two-step voltage flipping process is utilized to downsize the ponderous external inductor and extend application areas of such harvesting systems. SSHCI implementation with small flipping inductor-capacitor combination enhances voltage flipping efficiency and accordingly attains power extraction improvements over conventional synchronized switch harvesting on inductor (SSHI) circuits utilizing bulky external components. A novel MPPT system provides robustness of operation against changing load and excitation conditions. Innovation in MPPT comes from the refresh unit, which continually monitors excitation conditions of piezoelectric harvester to detect any change in optimum storage voltage. Compared with conventional circuits, optimal flipping detection inspired from active diode structures eliminates the need for external adjustment, delivering autonomy to SSHCI. Inductor sharing between SSHCI and MPPT reduces the number of external components. The circuit is fabricated in 180 nm CMOS technology with 1.23 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> active area, and is tested with custom MEMS piezoelectric harvester at its resonance frequency of 415 Hz. It is capable of extracting 5.44x more power compared to ideal FBR, while using $100~\mu $ H inductor. Due to reduction of losses through low power design techniques, measured power conversion efficiency of 83% is achieved at 3.2 V piezoelectric open circuit voltage amplitude. Boosting of power generation capacity in a low profile is a significant contribution of the design.

A Self-Powered Hybrid SSHI Circuit with a Wide Operation Range for Piezoelectric Energy Harvesting.

This paper presents a piezoelectric (PE) energy harvesting circuit, which integrates a Synchronized Switch Harvesting on Inductor (SSHI) circuit and a diode bridge rectifier. A typical SSHI circuit cannot transfer the power from a PE cantilever into the load when the rectified voltage is higher than a certain voltage. The proposed circuit addresses this problem. It uses the two resonant loops for flipping the capacitor voltage and energy transfer in each half cycle. One resonant loop is typically used for the parallel SSHI scheme, and the other for the series SSHI scheme. The hybrid SSHI circuit using the two resonant loops enables the proposed circuit’s output voltage to no longer be limited. The circuit is self-powered and has the capability of starting without the help of an external battery. Eleven simple discrete components prototyped the circuit. The experimental results show that, compared with the full-bridge (FB) circuit, the amount of power harvested from a PE cantilever and the Voltage Range of Interest (VRI) of the proposed circuit is increased by 2.9 times and by 4.4 times, respectively. A power conversion efficiency of 83.2% is achieved.

A Self-Powered and Area Efficient SSHI Rectifier for Piezoelectric Harvesters

This article presents an area efficient fully autonomous piezoelectric energy harvesting system to scavenge energy from periodic vibrations. Extraction rectifier utilized in the system is based on synchronized switch harvesting on inductor (SSHI) technique which enables system to outperform standard passive rectifiers. Compared to conventional SSHI circuits, enhanced SSHI (E-SSHI) system proposed in this paper uses a single low-profile external inductor in the range of $\mu \text{H}$ ’s to reduce overall system cost and volume, hence broadening application areas of such harvesting systems. Furthermore, E-SSHI does not include any negative voltage converter circuit and therefore, it offers area efficient AC/DC rectification. Detection of optimal voltage flipping times in E-SSHI technique is conducted autonomously without any external calibration. Energy transfer circuit provides control over how much energy is delivered from E-SSHI output to electronic load. The proposed system is fabricated in 180 nm CMOS process with 0.28 mm2 active area. It is tested using a commercial piezoelectric transducer MIDE V22BL with periodic excitation. Measured results reveal that E-SSHI circuit is capable of extracting up to 5.23 and 4.02 times more power compared with an ideal full-bridge rectifier at 0.87 V and 2.6 V piezoelectric open circuit voltage amplitudes (VOC, P), respectively. A maximum voltage flipping efficiency of 93% is observed at VOC,P = 3.6 V, owing to minimized losses on charge flipping path. Measured results are compared with state-of-the-art interface circuits. Comparison shows that E-SSHI design offers a huge step towards miniaturized harvesting systems thanks to its low-profile and fully autonomous design.

Piezoelectric energy enhancement strategy for active fuzzy harvester with time-varying and intermittent switching

This study aims to increase the amount of electrical energy harvested from a piezoelectric vibration energy harvester under unloaded and high-load resistance conditions. Although increased piezoelectric charge due to the synchronized switch harvesting on inductor (SSHI) strategy damps mechanical vibrations, the mechanical vibration amplitude of a mechanical element in a harvester is assumed to be constant for most discussions regarding the active harvester with SSHI strategy. However, this assumption is not valid under excessive switching actions, in which case the performance of the harvester deteriorates. This problem is known as the vibration suppression effect. To address this problem, in this study, two switching strategies for the charge inversion circuit—namely, switching considering vibration suppression-threshold (SCVS-t) and adaptive SCVS-t (ASCVS-t)—are proposed through intermittent switching actions. During the harvesting process, intermittent switching using these strategies is performed based on the output voltage threshold, thus maintaining high mechanical vibration amplitude and excellent harvesting performance by avoiding excess switching. The ASCVS-t adopts a tuning algorithm for the time-varying threshold and can achieve appropriate intermittent switching and effective harvesting under various vibration conditions without pre-tuning. Experimental comparisons with conventional strategies confirm that the proposed strategies achieve 2.9 times and 2.0 times greater harvested energy storages than a standard harvester and conventional switching strategy, respectively.

Design and Analysis of a Synchronized Interface Circuit for Triboelectric Energy Harvesting

This article reports the effectiveness of triboelectric energy harvesting using human motion by employing synchronous switch harvesting on inductors. The triboelectric nanogenerator (TENG) consists of an assembly of films of polytetraflouroethylene, nylon, copper, and aluminum, which produces and collects the charge during vertical motion. In order to improve and compare the electrical performance, the power generated through TENG was tested using a standard interface and series and parallel synchronized switch harvesting on inductor (SSHI) circuits. Our experimental results revealed that the series-SSHI circuit can significantly increase the amount of power extracted from triboelectric materials during walking. A peak DC output voltage of 32.78 V across 1 μF capacitance and 25 MΩ resistance and maximum power of 55.88 μW across a 10 MΩ resistance were achieved using a series-SSHI circuit. These results are significantly higher than those of a non-switched standard circuit without the use of inductors. We conclude that the continuous DC output obtained from human biomechanical energy at low frequency (6.5 Hz) can act as a reliable source for the sustainable operation of low power electronics.

Increased Piezoelectric Coupling Force in Autoparametric Excitation Harvester connecting to Self-powered Series and Parallel Synchronized Switch Harvesting on Inductor (SSHI) Interfaces

We experimentally investigate the relationship between the electromechanical coupling states, and the optimal resistive load, output power, and harvester’s displacement in the high output autoparametric excitation harvester connecting to the self-powered series and parallel synchronized switch harvesting on inductor (SSHI) interfaces. The piezoelectric coupling force increases as the acceleration and the resistive load increases, because the electromechanical coupling states enhances, as well as the piezoelectric voltage increases by the SSHI technique. The increased piezoelectric coupling force suppresses the harvester’s displacement, which leads to the shift in the optimal resistive load and the decrease in the output power. In our autoparametric excitation harvester, the parallel SSHI interface can achieve high output power at low acceleration, while the series SSHI can achieve high output power at high acceleration. The maximum output power of 3.1 mW was obtained at acceleration of 2.4 m/s2 (0.24G) by the series SSHI interface, from the overall harvester’s size 56×56×70 mm3.

Dual-stage Electrode Design of Rotational Electret Energy Harvester for Efficient Self-powered SSHI

This paper presents a dual-stage electrode design for electret-based rotational energy harvester (EH) to improve efficiency of synchronized switch harvesting on inductor (SSHI) technique. With the aid of the present parallel SSHI circuit, output power of the rotational electret EH developed in our group becomes 4.2 times higher if compared with the conventional full-bridge rectifier.

Synchronized Switch Harvesting on ElectroMagnetic System: a nonlinear technique for hybrid energy harvesting based on active inductance

This paper proposes a hybrid nonlinear interface combining both piezoelectric and electromagnetic effects for energy harvesting purposes. Based on the previously developed Synchronized Switch Harvesting on Inductor (SSHI) scheme, this technique aims at including as much as electroactive parts as possible, thus advantageously replacing the passive inductance in the SSHI approach by an electromagnetic transducer. The proposed scheme, called Synchronized Switch Harvesting on ElectroMagnetic system (SSH-EM) results in a significant increase of the output voltage, thus leading to a consequential increase of the harvested power, especially in the case of low-coupled systems, when compared to the classical SSHI approach and the standard approach (i.e., directly connecting the piezoelectric element to the load through a diode bridge rectifier and a smoothing capacitor). The working principle, along with theoretical developments, and supporting experimental results, are presented, both considering structures featuring constant displacement magnitude or structures driven at their resonance frequency with a constant excitation magnitude.

An Efficient Piezoelectric Energy Harvesting Interface Circuit Using a Sense-and-Set Rectifier

Piezoelectric energy harvesters (PEHs) are widely deployed in many self-sustaining systems, and proper rectifier circuits can significantly improve the energy conversion efficiency and, thus, increase the harvested energy. Various active rectifiers have been proposed in the past decade, such as synchronized switch harvesting on inductor (SSHI) and synchronous electric charge extraction (SECE). This article presents a sense-and-set (SaS) rectifier that achieves maximum-power-point-tracking (MPPT) of PEHs and maintains optimal energy extraction for different input excitation levels and output voltages. The proposed circuit is fabricated in the 0.18- $\mu \text{m}$ CMOS process with a 0.47-mm2 core area, a 230-nW active power, and a 7-nW leakage power. Measured with a commercial PEH device (Mide PPA-1022) at 85- and 60-Hz vibration frequency, the proposed circuit shows 512% and 541% power extraction improvement [figure of merit (FoM)] compared with an ideal full-bridge rectifier (FBR) for ON-resonance and OFF-resonance vibrations, respectively, while maintaining high efficiency across different input levels and PEH parameters.

A Self-Powered Piezoelectric Energy Harvesting Circuit With an Optimal Flipping Time SSHI and Maximum Power Point Tracking

This brief presents an ultra low power IC design for piezoelectric (PE) energy harvesting, which integrates a maximum power point tracking (MPPT) circuit and a synchronized switch harvesting on inductor (SSHI) circuit. The proposed circuit also has three different operation modes to extend the range of the harvestable power level generated by a PE transducer. The circuit is designed in CMOS and fabricated in BiCMOS 0.25 $\mu \text{m}$ technology with the die size of 2 mm2. The measurement results indicate the circuit can harvest energy with the input power ranging from 10 to 34 $\mu \text{W}$ during MPPT. It achieves peak efficiency of 77% under a PE cantilever voltage of 3.5 V and the battery voltage of 4.2 V.

Numerical modeling and analysis of self-powered synchronous switching circuit for the study of transient charging behavior of a vibration energy harvester

Enhancement of power harvesting efficiency in piezoelectric energy harvesters through a non-linear electronic interfacing circuit is a well-established research area with potentially significant implications on piezoelectric energy harvesting efficiency. Among various types of synchronous switching circuits available in the literature, a self-powered electronic breaker is widely studied. Nonetheless, due to the interdisciplinary nature of this field, many of the currently available analyses tend to overlook and/or simplify certain aspects of this dynamical system. As a result, a comprehensive model of the system that considers accurate coupling effect of the interfacing and storage circuitry, as well as detailed analysis of the system during transient capacitor charging and energy harvesting operation is still missing. This paper thus aims at the problem of modeling a piezoelectric energy harvester with an Synchronized Switch Harvesting on Inductor (SSHI) circuit and a self-powered electronic breaker. A semi-analytic numerical model is proposed that is able to accurately simulate the operation of the system during transient process of charging an external storage device. Experiment validation confirms the accuracy of the proposed model considering the exact electromechanical coupling effect and transient charging dynamics with SSHI circuit and the model’s performance in estimating system transient behavior. Furthermore, a systematic parametric study is performed in order to analyze the effects of different system components on the energy harvesting efficiency during transient operation.